As personal computers are widely used, a client and server system based on the personal computers now can handle tasks that were once possibly executed by a main frame computer system. Typically, a client and server system includes a high-speed server with a large-capacity auxiliary memory unit and a plurality of personal computers (clients). The server and personal computers are connected via a network, thereby allowing the clients to access the server. Specifically, each client has the ability to write and read information to and from the server and to exchange information with other clients connected to the network.
However, an increased number of clients create a bottleneck between a server and auxiliary memory units. As a result, access time would be longer and, worst, due to excessive load on the network, the network could be down or transmitted data could be lost.
In the client and server system, a hard disk drive (HDD) is dominantly used as an auxiliary memory unit. As is well known, the HDD is a large data storage device using magnetic disks. Data is stored to and read from a spinning disk by controllably positioning the read/write head over the disk. Thus, a reading/writing operation on the HDD requires a physical rotation of a motor and the lateral movement of the read/write head. In a server system such as game servers where tens of thousands of clients could simultaneously connect at one time, read and write requests from individual clients in the server can impose a serious load to the system. Servers with the HDD having a finite access time would not be able to handle ever increasing and faster data traffic. It could adversely affect the stabilization of the servers.
In a typical HDD, there is so-called access time, a time required to seek and change discs until a head is positioned over a sector. A drive motor is rotated to move the head over the sector where data is magnetically written and read. As is well known, while a high-performance SCSI bus provides a transmission rate of 320 Mega-bytes at the maximum, the HDD provides a transmission rate of 43 Mega-bytes at the maximum due to the aforementioned problems.
CPUs used in typical servers can address only up to several Giga-byte memory map ranges so that they cannot directly control a data storage capacity over tens of Giga-bytes reaching several Tera-bytes. Furthermore, the CPUs fail directly to drive a plurality of memories due to a fan-out between memory chips.